This invention relates to improvements in or relating to assembly line systems and is particularly concerned with conveyor chains used in such systems.
Cardanic conveyor chains are well known and may be utilised to carry pallets to various work stations along the assembly line, said pallets carrying workpieces to be operated on at the work stations.
In many known arrangements, the conveyor chains comprise chain links connected together in such manner that gaps occur in between the links on either side of the central axis of the conveyor chain, in order to allow the chain to follow a curved path in a generally horizontal plane. As the chain negotiates such a curved path the gaps on the inside of the curve tend to close whilst the gaps on the outside of the curve tend to open wider. Such gaps have been recognised as undesirable since it is possible that a finger, for example, could be trapped in such a gap and injured. Disadvantages of connecting together the links of the conveyor chain in such a manner that these gaps exist are discussed in Patent Specification No. WO 94/26636 and that Patent Specification outlines an arrangement including a disc-shaped element that covers the gaps during such relative rotation of the links in a horizontal plane. Other arrangements have been proposed for covering the gaps which include crescent fin-like projections that cover the gaps, although such proposals have been found to impose a restricted movement of the links relative to one another about a generally horizontal axis.
Whilst the arrangement shown in Patent Specification No. WO 94/26636 apparently shows an arrangement in which the movement about two mutually orthogonal axes is less restricted than some other arrangements including disc-shaped elements covering said gaps, it is believed that there still tend to be disadvantages with that arrangement.
For example, although the disc elements cover the gaps in the chain shown in WO 94/26636, the disc elements themselves are below the upper level of the chain thus creating shallow recesses an either side of the central axis of the chain which could lead to an ingress of dirt or other particulate matter. Furthermore, it is believed that the conveyor chain could be manufactured in a more efficient, simpler or cost-effective manner.